Subsea pipeline pig launching system

Claim 1

A pipeline pig launching system especially useful for launching at least one pig into a pipeline at a subsea location, the system comprising: (a) a tubular pig launch barrel having an upstream end, a downstream end, a bore extending between said ends, and means to connect the downstream end to a pig launch valve; (b) a tubular pig cartridge for loading with at least one pipeline pig in a press-fitted manner, said cartridge having an upstream end having a first outside diameter, a downstream end having a second outside diameter, a wall defining a bore of uniform inside diameter substantially the same as the diameter of the pipeline with which the system is employed, and means at said downstream end of said cartridge to seal said cartridge to the launch barrel, wherein said cartridge has a wall between its upstream and downstream ends with an outside diameter slightly less than said first and second outside diameters of said ends of said cartridge; (c) means for closing the upstream end of the launch barrel while the cartridge is in proper position in the barrel bore; and (d) means for inletting fluid pressure into the launch barrel bore for impelling a pipeline pig from the cartridge and through a launch valve into a pipeline to which the system is connected.